The proper time to have called the police was when you noticed the animal was off the leash roaming around freely in violation of the municipal code which you researched and can cite if need be, for starters.
In the situation, it would be after you have cleared leather the first time and gotten to safety. Call to make a report of the incident, because if it leads to something else you need to have a documentable trail of what happened to show whoever reviews the incident this is not some guy over-reacting to a dog, then getting into a shooting with his neighbors.
Police reports before a shooting prevent criminal cases after a shooting.
Further, you need to be sending a letter to the landlorg about the dangerous conditions he is allowing on his property and requesting a copy of the declerations page of his insurance to take to your attorney.
And talk to animal control next time you see the fucker roaming around. Because allowing a beloved pet to roam unprotected is wrong.
And make a call to the anti-blight people in town hall. I'm sure someone would love to go out to fine them $100/day over the uncut grass, trash not in bags and beer cans on the steps.